2.6. Other General Information
When cold bending plates or performing other operations involving cold bending and a sheared or flame-cut edge, care must be taken to preclude the initiation of cracks at the edge. Minimum inside radii for cold bending plates of various steel grades are indicated in ASTM A6 Appendix X4. It is indicated in the corresponding text therein that the tabular values may have to be increased when bend lines are parallel to the direction of final rolling or longer than 36 in. Additionally, the Manual states: “Flame-cut edges of hardenable steels should be machined or softened by heat treatment. Nicks should be ground out and sharp corners should be rounded.”
The maximum length of a fabricated assembly is primarily limited by shipping and erectability concerns, such as overall length and total weight. However, because individual practices and capabilities vary, it is best to consult with the fabricator directly.
The common solution to a member length concern is a splice, which may be necessary and/or desirable for fabrication, shipping and/or erectability considerations. When approved by the SER, fabricator-initiated splices in members are acceptable.
2.6.3. Common steel items, such as steel deck and openweb steel joists, are not considered to be structural steel in the 2010 AISC Code of Standard Practice. Why?
Even though items such as steel deck and open-web steel joists may be provided by the structural steel fabricator, they are not considered to be structural steel because they are neither manufactured nor fabricated by the structural steel fabricator. As such they are listed in Section 2.2 of the AISC Code of Standard Practice as “other steel, iron or metal items.” Items that are normally part of the fabricator’s work are listed as structural steel items in Section 2.1. of the AISC Code of Standard Practice.
Limits on radii of curved shapes are essentially a function of the capabilities of the bender. AISC does limit the radius of bend for bent plates to prevent cracking during the bending process. Though similar limits would apply to any bent product, such deformations are not generally achievable in HSS. Guidelines for bending plates are found in ASTM A6-Appendix X4.
Cold-bending guidelines for shapes are also found in the AISC Manual. They are summarized below:
1. The minimum radius for camber induced by cold-bending in members up to a nominal depth of 30 in. is between 10 and 14 times the depth of the member. Deeper members may require a larger minimum radius.
2. Cold-bending may be used to provide sweep in members to practically any radius desired.
3. A minimum length of 25 ft is commonly practical due to manufacturing/fabrication equipment. Bending by heat is also a possibility, but it should be noted that this procedure is generally much more expensive than cold-bending.
Note that providers for structural shape (including HSS) curving/bending often advertise their services in Modern Steel. A list of AISC Associate Member Bender-Rollers can be found at http://bit.ly/1ABwTV5. They would be the best ones to contact for determining minimum and maximum curved radii of shapes.